1-14 ANMAL Ki;i'(iUl OK I 1 1 IC Oft. Ooc. 



TUE FU.\CTIONS AND USES OF FOODS.* 



15 Y C. F. LANG WORTHY, I'll. IJ.. Office of Experiment Stations. 



Circular Xo. 46, United States Department of Agriculture. 



(Ordinary food materials, such as meat, lisli, eggs, potatoes, wheat, 

 etc., consist of — 



Refuse. — As the bones of meat and fish, shells of shellfish, skins 

 of potatoes, bran of wheat, etc. 



Edible portion. — As the fiesh of meat and fish, the white and 

 yolk of eggs, wheat flour, etc. The edible portion consists of water 

 and nutritive ingredients, or nutrients. The nutritive ingredients 

 are irroteln., fai'^', carbohydrates., and tnineral inattem. 



The water, refuse, and salt of salted meat and fish are called non- 

 nutrients. In comparing the values of different food materials for 

 nourishment they are left out of account. 



Use of Nutrients. 



Food is used in the body to build and repair tissue and to furnish 

 energy. The manner in which the valuable constituents are utilized 

 in the body may be expressed in tabular form as follows: 



Protein Forms tissue (muscles, tendon,! 



White (albumen) ot eggs, curd and probably fat) | 



(casein) of milk, lean meat, j 



grluten of wheat, eta | 



Fats Form fatty tissue I All serve as fuel and 



Fat of meat, butter, olive oil, yield energy in form 



oils of corn and wheat, etc. j. of heat and muscular 



Carbohydrates Transformed into fat. (strength. 



Sugar, starch, etc. j 



Mineral matters (ash). Aid in forming bone, assist in] 



Phosphates of lime, potash, soda, digestion, etc. 



etc. • j 



♦This article, which was orisinaUy published under the title "Foods for Man," in the 

 U. S. Dept. Agr. Yearbook, 1S9". pp. 676-6S2, has been revised and contains some additional 

 matter. 



The fuel value of food. — Heat and muscular power are forms 

 of force or energy. The energy- is developed as the food is con- 

 sum<'d in the body. The unit commonly used in this measurement 

 is the calorie, the amount of heat which would raise the temperature 

 of a jiound of water 4 degrees F. 



!iislr;i(l (»r this niiil, sdiiic iiuil of hum luniicii 1 ciicriix minlii 1„. 



